Driving system for diesel-electric vehicles



Feb. 17, 1970 H. ARNEMO 3,

DRIVING SYSTEM FOR DIESEL-ELECTRIC VEHICLES Filed Sept. 1. 1966 INVENTOR. #54 E 4/?4540 ArTme/VEXS United States Patent M US. Cl. 318-141 4 Claims ABSTRACT OF THE DISCLOSURE A diesel-electric traction system with a DC generator driving DC traction motors, in which the field excitation of the generator is controlled in response to the difference between a variable reference value and the actual value of the torque output of the diesel engine which drives the generator.

The present invention relates to a driving system for diesel electric vehicles. By diesel vehicle is here meant a vehicle which is driven by one or more electric motor connected to a generator driven by a diesel motor or the like.

With diesel motors and also with other combustion engines, the greatest safety in operation and the best economy is obtained if the motor as far as possible is driven at a certain constant speed. With a driving system according to the invention it is intended to obtain this result and at the same time to the greatest possible extent to derive full power from the diesel engine within the normal speed range of the traction motors-the variation of which can be of the order of 1 in 10 or 1 in 15with out using gear boxes or the like. At the same time a high degree of utilisation is obtained with the traction motors so that motors of relatively small type can be used. I A driving system according to the invention is based on the principle of using a diesel engine which is intended for constant speed, for example, a diesel engine which is provided with automatic control for constant speed, and to provide the diesel engine with a torque transducer which is included in a control system for controlling the excitation current of the generator in such a way that the delivered generator-current always corresponds to a chosen set value of the torque acting on the generator. Providing that the speed of the diesel engine is constant, its power can then be kept constant during long generating intervals.

The drawing shows schematically a driving system according to the invention.

In the drawing, 1 designates a diesel engine, 2 a magneto-elastic transducer arranged to measure the driving torque delivered by the diesel engine to the generator (that is, to indicate elastic shaft deformations), 3 a main generator which is a DC generator, 3a an excitation winding for the main generator 3, 4 a DC exciter intended for the excitation winding of the generator, 4a, 4b, 4c field windings for the exciter 4, and 5 and AC auxiliary generator intended for the magneto-elastic transducer 2, which is of a well known type needing AC current for its operation. Furthermore 6 designates an amplifier for the signals originating from the transducer 2, 7 a comparison device for forming the difference between the voltages originating from the amplifier 6 and the reference value device 22, 8 an amplifier for feeding the field windings 4b and 4c of the exciter 4, 9 a battery, 10 a switch gear for changing over between driving and braking. The driving system comprises four traction motors A, B, C, D, which are in- 3,496,439 Patented Feb. 17, 1970 tended for one vehicle wheel each. In said motors Ila-d designate the rotors, 12a-d the commutation windings, 13a-d series windings for the field systems and 14a-d shunt windings. 15a-d designate series-parallel switches for the shunt windings 14a d, 16a-d short circuit devices for the series windings 13a-d, 1'7a-d double-pole, double thraw; change-over switches for reversing the polarity of (11a+12a)(11d+12d), 19a-d brake resistors with contactors, 21a brake regulating resistor for 4a, 21b an adjusting resistor for 21a, 22a potentiometer resistor for operation 23 an adjusting resistor for 3a, 24 a driving pedal, 25 a brake pedal. All switches are shown in the normal driving position.

A driving system according to the invention comprises a diesel motor arranged to drive a generator with substantially constant speed, and at least one vehicle motor driven by the generator and a controlled current source connected to the excitation winding of the generator, characterised in that said driving system comprises an indicator for elastic shaft deformations, said indicator being arranged to constitute ,a transducer for the torque of the diesel motor, said transducer being connected to a comparison device, which is also connected to an adjustable reference value device, and arranged to supply the con trol circuit of said current source with an input magnitude corresponding to the difference between the output magnitudes of the reference value device and the transducer.

According to a further development of the invention the traction motors are made with a field system which is especially suitable when, at constant power, the greatest possible speed ranged is desired. As the requirement of constant power means that the required torque of the traction motors decreases an increasing speed, it is suitable to effect the highest speeds within the speed range of the traction motors by means of a reduction of the normal series fields. Instead of effecting such a reduction by connecting a parallel resistor, according to a further development of the invention such a reduction is obtained automatically and continuously in such a way that the field reduction increases as soon as the rotor voltage of the motor is increased in order to raise the speed. This is attained by providing the main poles of the motors with an auxiliary winding which counteracts the main winding, which is made like a series winding. The ampere turns of the auxiliary winding are proportional to the terminal voltage of the main generator. The demand for constant power in as large a part of the speed ranged as possible further means that, at low generator voltage and correspondingly low speed of the traction motor, the strongest possible motor field is desired. It is, however, not necessary to disconect the counteracting shunt winding as, at low speed, it does not cause any appreciable field reduction, partly because the series winding has maximum power so that the counteracting ampere turns of the shunt winding operate with small flow gradient, partly because the generator voltage supplied to the shunt winding is rather low at low speed.

With a driving system according to the invention it is intended, within the prescribed speed range for the vehicle (from 60 km./h. and down to a few km./h.) to derive an adjustable constant power from the diesel engine. The power level is to be adjusted with a pedal 24, which is used in a similar manner as the accelerator of a car. The controlled generator power is then fed to the four traction motors A, B, C, D which are connected in parallel with the generator 3.

The switch gear 10, which has three positions, is in neutral position when the vehicle is not in use and automatically moves to this position when the diesel engine stops, which is effected by means of a clamping arrangement not shown in the figure. If it is then desired to start and drive forward, the diesel engine is started and the handle for the switch gear 10 is placed in driving position, that is, with the contact arms in the position shown in the drawing. The series-parallel switches 15a-15d move simultaneously into driving position, that is with the contact arms in the position shown in the drawing so that the counteracting windings 14a14d constitute a series-connected group connected to the rotor terminals of the generator.

With the switch gear 10 in driving position the AC auxiliary generator feeds the magneto-elastic torque transmitter 2, which is connected to the input terminals of the amplifier 6, thus constituting a torsion indicator, the output terminals of which are connected to the comparison device 7, which is also given a signal from the reference device 22, in which the reference value is adjusted by means of a pedal 24. The comparison device 7 transmits the difference between the voltages from 6 and 22 to the input side of the amplifier 8 which is connected to the windings 4b and 4c with its output side. The amplifier 8 and the exciter 4 together form a controlled current source which delivers excitation current to the DC generator 3. Current is fed from the exciter 4 to the field 3a 0n the DC generator 3 so that a diesel engine power value corresponding to the position of the pedal 24 is reached. Balance then prevails in the comparison device 7 between the actual value originating from the torque transducer and the desired value in the reference device set by the pedal 24, aside from the small difference constituting the inherent signal error.

The driving direction of the vehicle, that is the direction of rotation of the friction motors, is determined by operation of the double-pole, double-throw switches 17a17d. When a driving direction opposite to that indicated by the arrows of the motor symbols is required, the movable pair of contact arms in each of the double-pole, double-throw switches 17a-17d are thrown over to their alternative contact making position, which is different from the position shown in the drawing. By this Operation, the direction of current is reversed in the rotor windings 11a-11d and the commutating windings 12a-12d, but maintained in the series windings 13(t-13d. During a normal start or operation the contacts 16a-16d are open. However, it can in unfavourable cases happen that, at the start, one of the wheels skids. It is then possible to overcome the skidding during the start by closing these contacts. Each wheel motor has its ampere meter 26 for main current indication so that it is possible to see how the motors work mutually. If a motor skids, its current falls as its speed rises. If, for example, it is the wheel of the A-motor which skids, it is possible to put the wheel and motor completely out of operation by closing contact 16a which is suitable if it is considered that for the moment the wheel cannot get any grip. The motors B, C, D now continue to work independently of A with somewhat increased torque. When the risk of skidding is probably past, 16a is opened again. Another way of removing the skidding when driving at relatively high speed is to reduce the speed on the skidding wheel so much that the friction between wheel and earth is capable of taking up the wheel torque. When, for example, the wheel of the A-motor skids, this can be effected by opening one of the contacts 19a, whereby the A- motor is series-connected with a resistor. In normal operation the contacts 19a-d are always closed.

When it is so required, electric braking can be effected by means of the system shown in the drawing, by making the traction motors work as generators which deliver effect to the brake resistors 19a-d. When electric braking is to be used, the switch gear is moved to braking position whereby the movable contact arms are pressed against the upper row of stationary contacts of the switch gear shown in the figure. The automatic system for the constant power regulation of the diesel engine is thereby put out of operation, and at the ame time the contact arms 4 of the series-parallel switches 15ad, shown in the figure, are set in vertical position whereby the shunt windings 14a-d are connected in parallel and connected to the rotor terminals of the exciter 4 through the switch gear 10. This exciter is now magnetized by the field winding 4a, which is connected to the battery 9 through the resistors 21a and 21b and the switch gear 10. During braking operation the series windings 13a-d are short circuited by means of the contacts 16a-d. All contactors within 19a-d are opened so that, in the first braking position (corresponding to the highest speed of the vehicle), the largest possible brake resistor is connected and all three resistance steps are connected to the brake regulation resistors 21a whereby the voltage on the traction motors working as generators is limited to a permissible value. As the speed falls a larger and larger part of the brake resistor 21a is short circuited by means of the brake pedal 25 and at the same time a larger and larger part of each of the brake resistors 19a-d is short-circuited by means of the cor-.

responding contactors.

The described regulation of constant power is considered to be possible down to to of maximum vehicle speed. At lower speeds and at standstill such a regulation without limiting the current could easily cause the traction motors to take up far more current than they can withstand. It is therefore necessary to provide a driving system according to the invention with a device which at standstill and very low speed automatically puts the constant power regulation out of operation and inserts a current limiting function.

The above suggested current limit regulation of the vehicle is not shown in the drawing but can be arranged as stated below.

It can be obtained by means of an electro-magnetic balance relay in the main circuit of the generator which for currents below a certain value has its arm in one direction a and when the current reaches a certain value the arm tilts in the other direction b. In position a the connection of the regulating equipment is as indicated in the drawing. In position b the connection is broken between 2 and 6 and instead the voltage from a resistor (measuring shunt), which is traversed by the main current, is led in to 6. At the same time as the input voltage to 6 is switched the connection indicated in the drawing is broken between the potentiometer 22 and the comparison device 7 and the latter is supplied with a constant comparison voltage corresponding to a maximum permissible current.

I claim:

1. Driving system for diesel-electric vehicles, which system comprises a generator, a diesel motor arranged to drive the generator with substantially constant speed, at least one vehicle motor driven by the generator, a controlled current source connected to the excitation winding of the generator, and a torsion indicator for elastic shaft deformations, said indicator constituting a transducer responsive to the torque of the diesel-motor, a comparison device, an adjustable reference value device, said transducer being connected to said comparison device and to said adjustable reference value device, said comparison device including means to supply the control circuit of said current source with an input magnitude corresponding to the difference between the output magnitudes of the reference value device and the transducer.

2. Driving system as claimed in claim 1, said driving motor being a DC motor whose field winding space is, for the most part occupied by a series-winding and additionally by a counteracting shunt-winding.

3. Driving system as claimed in claim 1, a plurality of parallel-connected driving motors being connected to the generator and each motor being provided with a means for indicating its load condition, and with connectable and disconnectable means for reducing the power supplied to the motor.

4. Driving system as claimed in claim 1, in which the driving system comprises an AC auxiliary generator which References Cited UNITED STATES PATENTS 4/1930 JeWitt 318-147 1/1964 Smith 31852 6 2,424,121 7/ 1947 Schlapfer 318147 2,454,778 11/ 1948 Curry 31-8147 ORIS L. RADER, Primary Examiner 5 K. L. CROSSON, Assistant Examiner U.S. Cl. X.R. 

